• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.606-609
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• 2008

Deconvolution is one of the most used techniques for processing seismic reflection data. It is applied to improve temporal resolution by wavelet shaping and removal of short period reverberations. Several deconvolution algorithms such as predicted, spike, minimum entropy deconvolution and so on has been proposed to obtain such above purposes. Among of them, $\iota_1$ norm proposed by Taylor et al., (1979) and used to compared to minimum entropy deconvolution by Sacchi et al., (1994) has given some advantages on time computing and high efficiency. Theoritically, the deconvolution can be considered as inversion technique to invert the single seismic trace to the reflectivity, but it has not been successfully adopted due to noisy signals of the real data set and unknown source wavelet. After stacking, the seismic traces are moved to zero offset, thus each seismic traces now can be a single trace that is created by convolving the seismic source wavelet and reflectivity. In this paper, the fundamental of $\iota_1$ norm deconvolution method will be introduced. The method will be tested by synthetic data and applied to improve the stacked section of gas hydrate.

• 자원환경지질
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• 제32권5호
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• pp.495-502
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• 1999

Common-mid-point (CMP) seismic data on a dipping layer have have a stacking different from a horizontal layer velocity and the reflection points on data are dispersed to many positions. Therefore, the CMP data are not stacked well by the conventional stacking method using the horizontal layer velocity. The CMP gather can ideally stacked by applying dip-moveout(DMO) processing. Hence, modern seismic processing indludes DMO as an essential routine step. DMO processing techniques are broadly categorized by two, Fourier transform and integral methods, each of which has many different computational schemes. In this study, the dip-decomposition technique of the Fourier transform method is used to test the DMO effect on the synthetic scismic data generated for dipping structures. Each of constnat offset sections NMO corrected by using the layer velocity of the model and DMO processed. The resulting zero-offset sections for many offsets are stacked. The stacked sections with DMO processing show the structural boundaries of the models much better than those without DMO processing.

• 지구물리와물리탐사
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• 제12권1호
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• pp.99-104
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• 2009

본 연구에서는 천부 토양층의 2차원 불균질 S파 단면을 결정하기 위해 천부 굴절법 탐사로부터 얻은 SH파 자료에 대한 파형역산 기법을 제안한다. 2차원 매질에서 SH파의 전파를 모사하기 위해 2.5차원 파동 방정식을 사용한다. 합성탄성파를 계산하기 위해 공간축으로 4차, 시간축으로 2차 근사한 staggered grid 유한차분법을 사용하여 파동 방정식을 푼다. 계산된 파형과 측정 파형의 잔여오차로 정의되는 목적함수를 하이브리드 발견적 탐색기법에 의해 최소화한다. 2차원 지하구조 모형은 각기 다른 심도 경계면을 갖는 블록과 블록 내부의 S파 속도에 의해 매개화한다. 수치실험은 암영층파 불규칙한 경계를 갖는 모델에 대해 백색잡음을 추가한 합성 SH파 자료를 이용하여 수행하였다. 지표 굴절법 자료로부터 암영층을 포함한 구조를 적절한 계산시간 내에 영상화할 수 있었다

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.156-157
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• 2005

Gas hydrate is ice-like crystalline lattice, formed at appropriate temperature and pressure, in which gas molecules are trapped. It is worldwide popular interesting subject as a potential energy. In korea, a seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. In this paper, we had conducted numerical and physical modeling experiments for seismic properties on gas hydrate with field data which had been acquired over the East sea in 1998. We used a finite difference seismic method with staggered grid for 2-D elastic wave equation to generate synthetic seismograms from multi-channel surface seismic survey, OBC(Ocean Bottom Cable) and VSP(Vertical Seismic Profiling). We developed the seismic physical modeling system which is simulated in the deep sea conditions and acquired the physical model data to the various source-receiver geometry. We carried out seismic complex analysis with the obtained data. In numerical and physical modeling data, we observed the phase reversal phenomenon of reflection wave at interface between the gas hydrate and free gas. In seismic physical modeling, seismic properties of the modeling material agree with the seismic velocity estimated from the travel time of reflection events. We could easily find out AVO(Amplitude Versus Offset) in the reflection strength profile through seismic complex analysis.

• Geomechanics and Engineering
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• 제37권6호
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• pp.539-554
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• 2024

This study explores development of prediction model for seismic site classification through the integration of machine learning techniques with horizontal-to-vertical spectral ratio (HVSR) methodologies. To improve model accuracy, the research employs outlier detection methods and, synthetic minority over-sampling technique (SMOTE) for data balance, and evaluates using seven machine learning models using seismic data from KiK-net. Notably, light gradient boosting method (LGBM), gradient boosting, and decision tree models exhibit improved performance when coupled with SMOTE, while Multiple linear regression (MLR) and Support vector machine (SVM) models show reduced efficacy. Outlier detection techniques significantly enhance accuracy, particularly for LGBM, gradient boosting, and voting boosting. The ensemble of LGBM with the isolation forest and SMOTE achieves the highest accuracy of 0.91, with LGBM and local outlier factor yielding the highest F1-score of 0.79. Consistently outperforming other models, LGBM proves most efficient for seismic site classification when supported by appropriate preprocessing procedures. These findings show the significance of outlier detection and data balancing for precise seismic soil classification prediction, offering insights and highlighting the potential of machine learning in optimizing site classification accuracy.

• 지질공학
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• 제27권4호
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• pp.513-518
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• 2017

Groundroll is a coherent noise showing dispersive behavior in land seismic-reflection records and its rejection has been a stubborn problem in data processing because they severely degrade the continuities and resolution of reflection signals. Conventional processing schemes of attenuating noises are the kind of frequency filtering (i.e., bandpass and f-k) that uses the Fourier transform (FT) along the entire trace in the time domain. To suppress them in this study, 1D wavelet filtering (WT) that can control time-varying frequency properties is tested and performed in the land-based synthetic and field seismic data. The results are compared to the ones from conventional filtering techniques in terms of continuities and resolution of reflection events. This filtering technique enhanced the reflection events by effectively eliminating the dispersive groundroll and random noises with control of time-scale function on wavelet domain.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.563-574
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• 2008

Most of earthquake-induced geotechnical hazards have been caused by the site effects relating to the amplification of ground motion, which are strongly influenced by the local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated GIS-based information system for geotechnical data, called geotechnical information system (GTIS), was constructed to establish a regional counterplan against earthquake-induced hazards at an urban area, Daejeon, which is represented as a hub of research and development in Korea. To build the GTIS for the area of interesting, pre-existing geotechnical data collections were performed across the extended area including the study area and a walk-over site survey was additionally carried out to acquire surface geo-knowledge data. For practical application of the GTIS used to estimate the site effects at the area of interesting, seismic microzoning map of the characteristic site period was created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation for site classification according to the spatial distribution of the site period was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site in the study area. Based on the case study on seismic zonations at Daejeon, it was verified that the GIS-based GTIS was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation.

• 자원환경지질
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• 제23권3호
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• pp.353-358
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• 1990

This paper presents numerical experiments on migration of synthetic seismograms using by $45^{\circ}$ wave equation. The seismograms used are zero-offset seismogram (corresponding to stacked section) on point reflectors, dipping plane reflector, faulted and folded layers. The seismograms are constructed by upward continuation of seismic source wavelets, exploading on subsurface reflection interfaces, to the earth surface. The synthetic seismograms are migrated by downward continuation and imaging. The upward and downward continuations are implemented by solving the $45^{\circ}$ wave equation with the finite-difference method. Migration of the synthetic data used in this study results in relatively accurate reposition of subsurface structures while the synthetic sections are quite different from the structures.

• 지구물리와물리탐사
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• 제6권1호
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• pp.13-22
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• 2003

TSP탐사는 터널 및 지하공간의 건설 시 굴착 진행 중인 터널 주위의 지질구조를 파악하기 위하여 VSP탐사를 터널 내에 적용한 물리탐사 기법이다. 하지만 터널 굴착예정 지역의 지질구조에 따른 터널 주위에서 파의 전파특성을 보여줄 수 있는 인공 탄성파합성 알고리듬이 부족한 실정이다. 이에 본 연구에서는 기존의 2차원 유한 요소 탄성파 모델링 알고리듬을 발전시켜 터널 전방에 여러 형태의 지질구조가 존재하는 경우에 대하여 2차원 시간영역 탄성파 모델링을 수행하였다. 그리고 이로부터 얻은 인공합성 탄성파단면과 파면단면을 통하여 파의 전파특성을 규명하고자 하였다. 우선 TSP탐사와 동일한 형태의 송수신 배열을 한 후, 균질 매질에 대한 모델링을 수행하여 인공합성 탄성파단면과 파면단면을 동시에 구해 직접파의 전파특성을 분석하였다. 그리고 터널 굴착방향과 수직인 반사면과 평행인 반사면이 존재하는 경우에 대해 각각 모델링을 수행하여 균질 매질의 경우와의 비교, 분석을 통해 반사파들의 전파특성을 고찰하였다. 또한 송신원을 수진기의 앞쪽과 뒤쪽에 배열한 두 가지 경우에 대하여 모델링을 수행하여, 두 방법의 특성과 장단점을 고찰하였다. 이와 같은 모델링을 통하여 TSP탐사자료의 해석, 역산 알고리듬의 개발 및 송수신 개발 등에 도움을 줄 수 있을 것으로 사료된다.

• 한국석유지질학회지
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• 제1권1호
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• pp.29-35
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• 1993

탄성파 트레이스 자료로부터 지구내부의 속도구조를 추정해내는 과정을 속도역산이라고 한다. 그러나 탄성파 트레이스자료가 담고 있는 정보의 주파수 대역은 제한되어 있으므로, 이것으로부터 광대역의 반사계수 수열을 구해내는 것은 쉽지가 않다. 본 연구에서는 선형 프로그래밍 처리기법을 이용하여 탄성파 트레이스의 진폭과 속도분석 자료를 적절히 결합함으로써 각 자료와 동일한 주파수 성분을 갖는 가장 단순한 형태의 속도구조를 구하고, 이것을 의속도 단면도로 도시하였다. 먼저 가상으로 설정한 모델로부터 프로그램의 효용성을 검증해 보았고 이를 토대로 우리나라 황해 제 2광구의 반사법 탄성파 자료에 적용하였다. 그리고 의속도 단면도와 이 지역에 위치한 시추공의 해석결과를 연관시켜 분석함으로써 백악기 화산암과 백악기 변성화산암의 경계를 구분하고 암상을 결정할 수 있었다.